1. Field of the Invention
The present invention relates to a urethane foam member of a nonrigid urethane foam, and to a seal structure, a toner storage container, a process cartridge and an image forming apparatus using the same.
2. Description of the Related Art
Nonrigid urethane foam (referred to below when appropriate simply as urethane foam) is foamed to several tens to several hundred times in volume by gas generation during forming, to give a nonrigid, extremely soft urethane foam with an extremely small bulk density. Such urethane foam is consequently used in various cushioning materials and seal members. However, potions of such urethane foam that are pressed in a heat press undergo permanent distortion, and therefore the value of such urethane foams for seal members is even greater.
An example of a urethane foam member that has undergone heat pressing applied as a seal member is, for example, a seal structure used in toner storage containers for copiers. Such a seal structure surrounds the periphery of a toner outlet, for supplying toner stored in the toner storage container, and prevents toner from flying around (see Japanese Patent Application Laid-Open (JP-A) No. 07-056430).
A related heat press urethane foam member 201 is shown in FIG. 15. The urethane foam member 201 is a structure in which a urethane foam 202 is heat pressed over the entire surface thereof by two flat plate heat presses 211, 212, and then cut to the desired shape and size. Permanent distortion is induced by heat in the urethane foam member 201, and in addition a thin resin layer 210a is formed on the surfaces thereof by the heat. When the urethane foam member 201 is made into a product by cutting into the desire shape using a press cutter or the like there is always a cut face C formed. Consequently when, for example, a resin or metal shutter, roller or the like (represented by a shutter below) contacts the obtained cut product on the face and moves to the left or right, a problem has been noticed of the shutter catching on an edge E of the cut face C obtained when making the product.
With air ducts, used for airflow paths of copiers and the like in order to suppress the rising in temperature within the apparatus, there is generally a complicated disposition of ducts within the apparatus, and there are often ducts configured by connecting together plural air ducts. When this occurs seal structures with seal members using urethane foam are often used at the connection portions of the duct. In such cases structures arise during assembly where alignment is by sliding along toward the opening portion of the ducts, as well as structures where alignment is from a direction perpendicular to the opening portion of the duct.
FIG. 16A and FIG. 16B show the above described seal member 210 obtained from urethane foam as an example of a seal structure used in an air duct of a copier. A rectangular opening 5a is opened in a unit 5 that is detachable from a non-illustrated copier main body, the structure such that by sliding in the direction of the arrow the unit 5 can be mounted to and detached and from an air duct 6 provided to the copier main body. The above seal member 210 made from urethane foam is adhered around the periphery of the opening 5a. 
When mounting, the face (cut face) along the thickness direction of the seal member 210 contacts the air duct first. Consequently the edge E of the seal member is sometimes lifted up.
An example of a seal structure, in which the air duct 6 is aligned from a direction perpendicular to the opening 5a, is shown in FIG. 17A and FIG. 17B. The urethane foam is compressed during mounting, deforming to the duct inside and the duct outside. There are cases in which the urethane foam sticks out, mainly at the cut face thereof (210x). Urethane foam members used between members that are frequently opened and closed, such as the front cover of a copier or the like, are likewise affected.
The common problem with the use of seal members made from urethane foam for such portions is that the cut face portions of the urethane foam become obstacles. In the present invention the seal member is one obtained by heat pressing urethane foam, and provides a seal member and a seal structure capable of suppressing catching on the edge thereof.